Comparative transcriptomic analysis of Glycine soja and G. max and functional identification of GsCNGC20-d interacted with GsCDPK29 under salt stress

Cyclic nucleotide-gated channels (CNGCs) in plants are nonselective Ca2+-permeable cation channels, and are involved in the regulation of plant growth, development and response to stressful environments. However, the functions and molecular mechanisms of CNGCs in soybean under salt stress remain largely unknown. Here, the CNGC family member GsCNGC20-d that is specifically upregulated in the roots of the salt-tolerant G. soja BB52 accession was identified by comparative transcriptomic analysis with the salt-sensitive G. max N23674 cultivar. The GsCNGC20-d protein was localized in the plasma membrane (PM). GsCNGC20-d-overexpressed hairy-root composite soybean plants and transgenic Arabidopsis exhibited enhanced salt tolerance, which was reflected by maintaining higher [Ca2+]cyt and antioxidant activities of POD and CAT as well as lower shoot Na+/K+ ratios, and activating the expression of salt stress-related genes (SOS1–3, SALT3, NHX1, RbohB, CAT1/3 and POD). Moreover, the identified protein kinase GsCDPK29 exhibited an interaction with GsCNGC20-d in Y2H, LUC and BiFC assays. GsCNGC20-d/GsCDPK29 co-overexpressed hairy-root composite soybean plants displayed enhanced salt tolerance through their synergistic effects on the increases of [Ca2+]cyt in root tips and antioxidant activities of POD and CAT, the maintenance of lower MDA content in roots and leaves, and Na+/K+ ratio in shoots. The synergistic regulation of GsCNGC20-d and GsCDPK29 involved in the response and adaptation of salt-tolerant G. soja BB52 to salt stress, will provide new perspectives for further understanding the molecular mechanism of salt tolerance in G. soja and the molecular breeding of salt-tolerant G. max or other crops.